Fog abatement

ABSTRACT

A method and apparatus for increasing visibility through fog by employing an electrical field to force liquid particles in the fog together to form large drops of sufficient mass to precipitate from the fog under the force of gravity.

United States Patent [72] inventor William A. Hall Springfield, Pa.

25,070 Apr. 2, 1970 Aug. 17, 1971 Atlantic Rlehfleld Company New York,N.Y.

[21-] Appl. No. [22] Filed [45] Patented [73] Assignee [s4 rot;ABA'IEMENT 8'Clalms, 3 Drawing Figs.

52 use! ss/s,ss/123.9s/mo. 1 7 B03: 3/00 [50] Field olSearch 317/262 R;

98/1,DIG. 1;55/107, 122,123, 5,10,18

[56] References Cited UNITED STATES PATENTS 1,120,560 12/1914 Strong3l7/262X Primary Examiner-William H. Beha, Jr. Assistant Examiner-HarryE. Moose, Jr. Attorneys-Blucher S. Tharp and Roderick W. MacDonaldABSTRACT: A method and apparatus for increasing visibility through fogbyemploying an electrical field to force liquid particles in the fogtogether to form large drops of sufficient mass to precipitate fromthefog under the force of gravity.

PATENTEU AUG I 7 I9?! sum 1 or 2 FIG. 2

FIG.

IN/ENTQF' WILLIAM A. HALL fldM-J/M%@ 2g ATTORNEY PATENTEU Wm SHEET 2 [IF2 FIG. 3

INVENTOP WILLIAM A. HALL AT TOHNEY I rocanxrnmm'r BACKGROUND or Tit-r;INVENTION Water cooling towers. and otherapparatus normally associatedwith industrial plants emit an air stream in large volume, i.e. hundredsof thousands bf cubic feet per minute. The air stream is at atemperature substantially above normal ambient conditions, particularlyin 'the winter time. The air stream is alsosaturated with water vaporand contains some entrained water particles. i

Thus, when the heated, water-laden air from its source mixes with and isdiluted by ambient air just outside the source, water condensesfromtheair and forms a dense fog or it is highly desirable to have amethod for reducing. the fog.-

density and thereby increasing the: visibility through'that fog; Themethod should. be economical, uncomplicated inform,- anditself-nonpolluting.

I-Ieretofore, burners have been employed to heat the water saturated airas it passes from its source. Electrostatic precipitation of thewaterfromthe'air is not consideredpractical because the volume and speed ofthe'water-laden air'leaving the source is too great for a precipitatorof anywhere near conventional size to remove the water therefrom. Inother words, it would take too large a precipitator apparatus to allowall the water carried by the air to coagulate on-the col 'lectorelectrode of the precipitatorwtobedrainedidownthat 2 This invention isuseful in reducing the density and increasing the visibility through thefog formed fr orn oneor more liquids so'long'as' at least one of theliquids is sufii ciently electrically active to be movable under theforce of an electrical 5 field. Thus, this invention is applicable tofogs containing electrode into a sump. This'isthe-normal operation for aprecipitator, i.e.'the particles in the "gas streamare pushed bythe'coro'na. (electricaltield) away from the discharge elec trode towardthe collecting electrode to becaught by the col lecting: electrode andremoved therefrom. Thus, electrostatic precipitators in their normaloperation are considered not suitable for solvingthis problem. a

SUMMARY on THE INVENTION from thefog on an electrode, but rather theliquid particlesin the fog are forced' closer togetherto. cause themto..coalesceinto larger drops which rain out ofr the fog-Thisreducesthe' densityof the fog;and.increasesthevisibilitytherethroughi' It should be-understood that. thisinvention'does not primarily, byway of itselectrical'field, cause theremovalof 'wateror otherliquid from a fog by way, of the-"liquid"collectingaon the collector electrode-as is normal for'electrostatic.precipitators.

The electrical field of this invention' coalesces liquid particles inthefog, so that they rain; out of the-fogafter thefog has left the vicinityof the .electrical'field andthe electrodes.

Accordingly, inaddition to a .methodjfor-coalescing llquid particles ina fogto subsequentlyrain out ofthe fog'and clarify same, this inventionrelates to apparatus for reducingfogjdem sity from anoutletbthereof'utilizingratxleast one-pair of-electrode meansarrangedinamanner relative to the fog OutltfSO that at least partof the fogxpasses. between the3eltt0da means.

liquid particles other than or in additiontoiwater. However, thisinvention is particularly applicable to the abatement of water fog,particularly from apparatus sources such as water cooling't'owers.

Accordingly, an object of this invention is to provide a new andimproved method 'for fog abatement. Another object is to provide a newand improved method for coalescing liquid particles in a fog. Anotherobject is a new and improved method for" utilizing electrical fields tocause the formation of liquid drops in a fog of sufiicient mass to rainout of the fog under the force of gravity. Another object is to provideanew and improved apparatus for treating fog to reduce the densitythereof and to increase the visibility therethrough'. It is anotherobject to provide a new and improved apparatus for coalescing liquidparticles in a fog. Another object is a new and improved method andapparatus for reducing water fog emitted by water cooling towers. v

Other aspects, objects, and'advantages of this invention will beapparent to those skilled in the art from this disclosure and theappended claims. I

DETAILED DESCRIPTION OF THE INVENTION FIGS. 1 through 3 show elevationaland plane views of a conventional water coolingtower employing oneembodiment of this invention. a

Morespecifically, FIG. 1 showsan elevational view of one cell of aconventional counter flow, induced draft cooling tower l which has abottom section 2, main walls 3, and a top section 4.

Topsection 4includes a fan space 5 surmounted by a fan stack6. Fan spaceScontains a conventional fan 7 powered by motor means 8; Motor 8 isoperatively connected by drive shaft '9 to a conventional gear box 10.Fan shaft 11 is operativeIy connected to gear box'10. IThelower'portionof main walls 3 contains air intake louvers (not shown)through which'air is drawn, as shown by arrows 13 and" 14, fromoutsidethe cooling tower into a lower portion'thereof and upwardly toward fan 7Water enters in theupper portion of the cooling tower by way ofpipe 15"and is sprayed downwardly toward the incomingair by way of a pluralityof spray nozzles 16. In this manner thewater iscooled by contact withthe air. The air becomes saturatedwith water vapor and picks up someentrained water particles. The water is collected at bottom 2 andremoved by conventional meansnot shown.

The water saturated air continues upwardly through fan stack 6 a's shownby arrow 17 and outwardly where it is mixed with" and diluted by outsideair which is 'at an ambient temperature.

Normally, the water to be cooled" in pipe 15 is at a temperature of atleast'about 100 F. and the water saturated air leaving fan stack 6'is atatemperature of at least about F. In situations where the ambienttemperature is less than 90 F. and/or theambient air'has a highhumidity, i.e. from 60 to percent humidity, the water dissolved in thefan stack air will condense in'area' I8 and form a dense fog representedby undulating'lines 191 1 FIG: 1"showsa windblowing in the direction ofarrow 20 so that fogal9is blown toward'a'pluralityofpairs of electrodes21 mounted on sidewall 3. Electrodes 21 extend upwardly, toward, andover fan'stack 6but are spaced therefrom a sufficientdistance so thatfog can first form in area 18.

As 'an'additionalembodiment tothebasic invention hereof, another pipe22' extends inwardly into tower 1 and carries spray nozzles 23 which areadapted to disperse a desired additiveinto theairwhich will ultimatelybe emitted from fan stack 6." As will'be discussed in more detailhereinafter, pipe than the other so that a corona or electrical fieldis" established. The electrode at the higher potential is the dischargeelectrode and the electrode at the lower potential is the collectingelectrode in the normal sense, but not in the sense of this invention inthatin this invention a collecting electrode is not used for collectingliquid'from the fog passing thereby.

As fog 19 passes between the two electrodes, the liquid particles in thefog are acted upon by the electrical field and forced closer to oneanother so that a substantial numberof these particles coalesce with oneanother to form larger liquid drops. These liquid drops are then ofsufficient mass that the force of gravity acting thereon overcomes thecarrying force of the mass velocity of the fog and the larger drops rainout after leaving electrodes 21 as shown by reference numeral 25.

Thus, the collecting electrodes in each pair 30 do not take liquid fromthe fog but merely cause coalescence of liquid particles in the fog tocause liquid drop rain out afterleaving electrodes 21. By inducingcoalescence of liquid particles and by allowing the subsequent rainingout of these particles, the fog density is substantially decreased and,therefore, the visibility through the fog is substantially increased.

FIG. 2 shows a plane view of the tower of FIG. 1 and shows a pluralityof pairs of electrodes 30 arranged along side 31 of main wall 3. Eachpair 30 is connected in a manner discussed hereinafter in detail in inFIG. 3 so that one is at a higher potential than the other. By theionizing effect of the electrical field on the liquid particles in thefog, the particles are agitated and collide with one another and in sodoing coalesce. Put another way, momentum transfer of ions streamingfrom the discharge or higher potential electrode to the collectingelectrode produces a lateral motion of the liquid particles between theelectrode by the electric wind passing from the discharge electrode tothe other electrode. However, the coalesced liquid particles do notcollect to a substantial degree on the collecting electrode as in thenormal electrostatic precipitator operation but rather leave theelectrical field in the coalesced condition. Thus, the electrical fieldstrength is controlled so that the liquid particles in the fog areforced together to form larger liquid drops but without causingsubstantial amounts of liquid condensation on the collecting electrode.This is quite different from normal electrostatic precipitatoroperation.

Depending upon the ambient atmosphere and its physical conditions, thecomposition of the fog, the configuration and relationship of theelectrodes to one another, and the like, an electric field strengthsuitable for this invention can vary widely but generally is that whichwill cause-the liquid particles in the fog to be forced together in themanner described above. Generally, the electrical potential differencebetween. two electrodes of each pair 30 should be at least about 5000volts per inch of spacing between the two electrodes. The electricalpotential difference can be established using either a direct current oralternating current, as desired.

The electrical conductivity of the fog can further be improved so thatthe liquid particles in the fog will be more subject to being moved bythe action of the electrical field by introducing a suitable additivematerial by way of pipe 22 and the two electrodes. Generally, finiteamounts up to about 100 parts per million, preferably up to about partsper million, can be employed.

FIG. 3 shows. the cooling tower of FIGS. 1 and 2 viewed toward side 31of FIG. 2 so that the pairs of electrodes 30 can be seen. Each pair ofelectrodes iscomposed of a discharge electrode 40 and acollectingelectrodefll Discharge electrodes 40 are electricallyconnected by means ,of wire 42 to rectifier 43 which in turn iselectrically connected by wire 44 to a voltage source 45. Collectingelectrodes 41 are operatively connected by means of wire 46 to ground.Thus, an electric field is set up between electrodes 40 and 41 in eachpair of electrodes 30 so that substantially all fog passing from fanstack 6 passes through an electric field. I

The electrodes can be mounted on main walls 3 of the cooling tower or'onthe periphery of fan stack 6 or any combination thereof. The electrodescan completely surround the fan nozzles 23 (FIG. 1). A suitable additiveor additives will vary widely depending upon the materials being treatedand-the like but will generally be a material which itself is subject toionization by the electric field. For example, ammonia or ammonium saltssuch as ammonium halides (particularly ammonium chloride), ammoniumsulfate, ammonium nitrate, and the like, can be employed. Of course,mixtures of two or more of these materials can be used. These additivesare normally employed in amounts effective to increase the amount ofcoalescence of liquid particles in the fog passing: between stack orextend around any desired portion thereof. For example, the electrodescan be disposed on one side as shown in FIG. 3 or two or three or allsides, as desired.

The electrodes themselves can be of any conventional configuration. Forexample, the discharge electrode will normally be a wire or plate andthe collecting electrodes can be a rod curtain, a corrugated plate, dualperforated plates, plates with fins to increase surface area, and thelike. Various electrode combinations and configurations as well as theconventional methods by which they can be connected to one another andoperated to establish an electrical field therebetween are fully andcompletely disclosed in an engineering report prepared for the AmericanPetroleum Institute entitled Removal of Particulate Matter from GaseousWaste-Electrostatic Precipitators," 1961, American Petroleum Institute,Division of Refining, 1271 Avenue of the Americas, New York, New York.The subject matter of this report is incorporated herein by reference.

EXAMPLE A water cooling tower substantially as shown in the drawings isused to cool heated water from a catalytic cracking unit. The coolingtower is designed to remove 300 million B.t.u. per hour from 24,000gallons per minute of water introduced by pipe 15. The water enters thecooling tower at about 100 F falls downwardly in the cooling tower,contacts upcoming ambient air, saturates the upcoming air with water,and heats the upcoming air to about F.

When the ambient conditions around fan stack 6 are such that the ambientair is at a temperature lower than 90 F. and theambient humidity isabout percent, the heated, water saturated air emitted from the top offan stack 6, after mixing with ambient air, forms a dense fog because ofthe precipitation of water from the heated, saturated air as it iscooled by the ambient air.

Pairs' of electrodes substantially as that shown in the drawings areemployed, each pair having an electrical potential difference of about5000 volts per inch of spacing between electrodes. That portion of fogpassing between two electrodes of each pair of electrodes has asubstantial portion of its fog forming particles forced into contactwith one another to coalesce same into raindrop size liquid drops. Thedrops rain out of the fog primarily after the fog has left the vicinityof the electrodes and the influence of electric field between thoseelectrodes. The degree of fog density decrease and visibility increaseis varied widely by varying the strength of the electric field betweenthe electrodes and the electrical conductivity of the fog itself. I

. Reasonable variations and modifications are possible within one pairof electrodes, establishing an electrical potential dif ference betweenthe two electrodes of each pair of electrodes Q so that an electricalfield is established between the two electrodes by the electrode whichis at the higher potential, controlling the electrical field strength sothat liquid particles in said fog are forced together -to form largerliquid drops without collecting on an electrode, said larger liquiddrops being of sufficient mass to precipitate from said fog due to theforce of gravity after leaving said electricalfield. v

2. in a method for reducing fog density from a source thereof toincrease visibility therethrough; the improvement comprising dispersingin said fog an additive which improves the electrical conductivity ofsaid fog, passing at least part of said fog between at least one pair ofelectrodes, establishing an electrical potential difference between thetwo electrodes of each pair of electrodes so that an electrical field isestablished between the two electrodes by the electrode which is at thehigher potential, controlling the electrical field strength so thatliquid particles in said fog are forced together to form larger liquiddrops without collecting on an electrode, said larger liquid drops beingof sufficient mass to precipitate from said fog due to the force ofgravity after leaving the electrical least one of ammonia and ammoniumsalts.

7. A method according to claim 2 wherein said ammonia is present infinite amounts up to about 10 parts of ammonia per million parts ofwater in said fog.

8. A method according to claim 2 wherein said electrical potentialdifference is established using alternating current.

1. In a method for reducing fog density from a source thereof toincrease visibility therethrough, the improvement comprising passing atleast part of said fog between at least one pair of electrodes,establishing an electrical potential difference between the twoelectrodes of each pair of electrodes so that an electrical field isestablished between the two electrodes by the electrode which is at thehigher potential, controlling the electrical field strength so thatliquid particles in said fog are forced together to form larger liquiddrops without collecting on an electrode, said larger liquid drops beingof sufficient mass to precipitate from said fog due to the force ofgravity after leaving said electrical field.
 2. In a method for reducingfog density from a source thereof to increase visibility therethrough,the improvement comprising dispersing in said fog an additive whichimproves the electrical conductivity of said fog, passing at least partof said fog between at least one pair of electrodes, establishing anelectrical potential difference between the two electrodes of each pairof electrodes so that an electrical field is established between the twoelectrodes by the electrode which is at the higher potential,controlling the electrical field strength so that liquid particles insaid fog are forced together to form larger liquid drops withoutcollecting on an electrode, said larger liquid drops being of sufficientmass to precipitate from said fog due to the force of gravity afterleaving the electrical field.
 3. A method according to claim 2 whereinsaid fog is a water fog and the fog source is a water cooling tower. 4.A method according to claim 2 wherein said electrical potentialdifference is at least about 5000 volts per inch of spacing between thetwo electrodes of each pair of electrodes.
 5. A method according toclaim 2 wherein said electrical potential difference is establishedusing direct current.
 6. A method according to claim 2 wherein saidmaterial is at least one of ammonia and ammonium salts.
 7. A methodaccording to claim 2 wherein said ammonia is present in finite amountsup to about 10 parts of ammonia per million parts of water in said fog.8. A method according to claim 2 wherein said electrical potentialdifference is established using alternating current.